/*
 * Anything: A flexible and easy to use data structure that combines the 
 * characteristics of a list and a hashmap into one data structure.
 * 
 * Based on a paper by Peter Sommerlad and Marcel Rueedi on 
 * 'Do-it-yourself reflection' entered at EuroPLOP 1998.
 * 
 * This library was written completely from scratch and is based only 
 * in spirit on the original Java Anything implementation written by 
 * Andre Weinand/Marcel Rueedi in 1997/99 and enhanced by Stefan Tramm 
 * in 2006.
 * 
 * Copyright (c) 2008 Thomas Marti and others. All rights reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package any.functor.impl.pred;

import any.functor.interfaces.Predicate;

public class CorePredicates {
	
	private static final Predicate<?> ALWAYS_TRUE = new BasePredicateWithDescription<Object>("ALWAYS_TRUE") {
		public boolean apply(Object any){
			return true;
		}
	};
	
	private static final Predicate<?> ALWAYS_FALSE = new BasePredicateWithDescription<Object>("ALWAYS_FALSE") {
		public boolean apply(Object any){
			return false;
		}
	};
	
	// ----------------------------------------------------------------------------------------
	
	@SuppressWarnings("unchecked")
	public static <T> Predicate<T> alwaysTrue() {
		return (Predicate<T>)ALWAYS_TRUE;
	}

	@SuppressWarnings("unchecked")
	public static <T> Predicate<T> alwaysFalse() {
		return (Predicate<T>)ALWAYS_FALSE;
	}
	
	public static <T> Predicate<T> not(final Predicate<T> predicate) throws NullPointerException {
		if (predicate == null) throw new NullPointerException();
		return new BasePredicate<T>() {
			public boolean apply(T t) {
				return !predicate.apply(t);
			}
			@Override public String toString() {
				return "not " + predicate;
			}
		};
	}
	
}
